The present invention relates to a liquid crystal display device having tape carrier packages, and more particularly, to a large liquid crystal display device whose architrave portion is small.
Conventional liquid crystal display devices may be roughly categorized into a simple matrix liquid crystal display device, arranged so as to drive pixels at intersections of striped X and Y electrodes, and an active matrix liquid crystal display device having an active element, e.g. a thin film transistor, per pixel and arranged so as to switch and drive the active elements.
As shown in FIG. 23, the typical liquid crystal display device is provided with a driving circuit board 524 (which is divided into three driving circuit boards 524a, 524b and 524c in general) around a liquid crystal panel 503 to supply imaging signals to imaging pixels within the panel. Each one of the driving circuit boards 524a, 524b and 524c is provided along a respective side of the liquid crystal panel 503, and they are electrically connected to each other by a flat cable 536. Tape carrier packages 535a, 535b and 535c and electronic parts, such as a resistor and a capacitor, are mounted on each one of the driving circuit boards 524a, 524b and 524c, and IC chips (semiconductor chips) 537a, 537b and 537c for driving the liquid crystal panel 503 are mounted on each one of the tape carrier packages 535a, 535b and 535c by means of tape automated bonding (TAB).
Each of the tape carrier packages 535a and 535b forms one of the segment drivers IC-U1 through Un and IC-L1 through Ln, respectively, to be described later, and each tape carrier package 535c forms one of the common drivers IC-C1 through Cn, to be described later. In this example, the IC chips 537a and 537b mounted on the tape carrier packages 535a and 535b, respectively, are provided with a circuit shown in FIG. 20, to be described later, i.e. an input side bonding pad of the IC chip, a random logic circuit 510, a shift register circuit 511, a bit latch circuit 512, a line latch circuit 513, a selector circuit 514, an output buffer circuit 515 and an output side bonding pad, disposed in order along the direction of the flow of signals (data).
FIG. 24 is a section view of the prior art tape carrier package 535a. In the figure, the reference numeral 541 denotes an input side wire of the IC chip 537a and 542 denotes an output side wire. An input side bonding pad 543a of the IC chip 537a is connected with an inner lead of the input side wire 541 and an output side bonding pad 543b is connected with an inner lead of the output side wire 542 by so-called gang bonding. Here, the input side wire 541 and the output side wire 542 are made of copper (Cu) for example.
Outer leads of the input side wire 541 and the output side wire 542 correspond to input and output terminals of the IC chip 537a, respectively, and the outer lead of the input side wire 541 is connected with a terminal of the driving circuit board 524aby soldering or the like, while the outer lead of the output side wire 542 is connected with a terminal of the liquid crystal panel 503 by an anisotropic conductive film. A base film 544 is made of polyimide or the like and is bonded with the input side wire 541 and the output side wire 542 by adhesive 545. There are also provided a solder resist film 546 for masking so that no solder is applied unnecessarily during soldering and a thermosetting resin 547 for protecting the IC chip 537a. Such a protecting member is described in Japanese Patent Laid-Open Nos. Hei. 4-42547 and Hei. 8-43843.
FIG. 25 is a diagrammatic enlarged view of the tape carrier package 535a shown in FIG. 23. It is noted that FIG. 25 shows a state in which the thermosetting resin 547 for protecting the IC chip 537a is removed in order to facilitate an understanding thereof.
Because the pitch of the terminals (segment electrode terminals) of the liquid crystal panel 503 is different from the pitch of the output side bonding pads 543b, the output side wires 542 of the tape carrier package 535a are slanted such that the pitch thereof becomes narrow along the wires from the outer leads thereof where the pitch is wide to the inner leads where the pitch is narrow, as shown in FIG. 25. A similar slanted wiring arrangement is required more or less also for the input side wire 541 of the tape carrier package 535a. Thus, the use of slanted wires 548a and 548b has been necessary in the input side wire section 541 and the output side wire section 542 of the tape carrier package 535a in order to adjust the pitches at each lead of the input side wire 541 and the output side wire 542.
There has been a tendency to increase the size of the display screen lately with respect to the overall size of the liquid crystal display device, such as a liquid crystal display module (LCM), and, for this purpose, there is an increased demand to reduce an area outside the display area of the liquid crystal display device, i.e. the architrave portion thereof, as much as possible in order to eliminate useless space and to give the display a fine appearance. While it is desirable to reduce the area around a display window of an upper frame 521, as shown in FIG. 22, to be described later, in order to reduce the architrave portion of the liquid crystal display module (LCM), the tape carrier packages 535 and the driving circuit board 524 are located in the area around the display window of the upper frame 521. Therefore, to achieve this objective, it is necessary to miniaturize the tape carrier packages 535 and the driving circuit board 524 located in the area on and under the upper frame 521 in order to reduce the architrave portion on and under the liquid crystal display module (LCM). For this purpose, it is conceivable to (1) miniaturize the electronic parts disposed on the driving circuit board 524, to reduce a number of the electronic parts or to reorganize the layout thereof, or (2) miniaturize the tape carrier packages 535 to provide enough space for the electronic parts to be disposed on the driving circuit board 524, while permitting the display window to be enlarged as much as possible.
However, the organization in mounting the electronic parts on the driving circuit board 524 in the above-mentioned proposal (1) seems to have reached its limit, so that the tape carrier package 535 has to be miniaturized as described above in the proposal (2). Especially, the length (TCP width) of the tape carrier packages 535a and 535b in the direction of wiring, i.e. the input side wire 541 and the output side wire 542, must to be reduced. However, it has been difficult to reduce the length of the conventional tape carrier packages 535a and 535b in the wiring direction for the following reasons:
(1) Because the terminal of the driving circuit board 524 and the terminal of the liquid crystal panel 503 are connected to the outer leads of the input side wire 541 and the output side wire 542 of the tape carrier packages 535a and 535b, the outer leads of the input side wire 541 and the output side wire 542 of the tape carrier packages 535a and 535b must have a certain minimum length that fully assures the reliability of the connection.
Further, the slanted wires 548a and 548b of a predetermined length are necessary in order to adjust the pitch at each lead of the input side wire 541 and the output side wire 542 with respect to the input side wire 541 and the output side wire 542 of the tape carrier packages 535a and 535b.
Under such a presupposition, when the size of the display screen of the liquid crystal display device is increased and the pitch size of the outer leads of the output side wire 542 of the tape carrier packages 535a and 535b is increased (or the size of the IC chips 537a and 537b is reduced and the pitch size of the inner leads of the output side wires 542 of the tape carrier packages 535a and 535b is reduced), the wire extending length (LO) of the slanted wire 548b of the output side wire 542 of the tape carrier packages 535a and 535b increases. Especially, because the pitch (e.g. 90 to 95 .mu.m) and the number (e.g. 240) of the electrodes which extend from the inside of the liquid crystal display device is set without direct connection with the mounting on the tape carrier package, the slanted wiring section of the output side wire is essential in the connection with the pitch (e.g. 80 to 85 .mu.m) of the output terminals of the semiconductor chip.
It is noted, that although the same applies to the pitch of the input terminals of the semiconductor chip, similarly to the output terminals, a number of dummy input terminals which do not contribute to the display are generally provided. While the input terminals including such dummy terminals are connected with the same number of input side wires at an opening of the package, they connect to the input side wire or another dummy terminals on the middle of the film and a fewer number of input side wires (e.g. 30) are connected with the terminals of the driving circuit board and contribute to the signal input, so that the slanted wiring section of input side wires is not always necessary.
(2) Dummy input side bonding pads are provided on the semiconductor chips 537a and 537b and these dummy input side bonding pads are connected to an NC pin (a dead pin or dummy pin) in the input side wiring section of the tape carrier packages 535a and 535b in the prior art tape carrier package.s 535a and 535b in order to assure the uniformity of the inner leads of the input side wire 541 and the output side wire 542 during the bonding thereof.
In this case, although a protecting diode is provided on the normal input side bonding pad 543a, no protecting diode is provided on the dummy input side bonding pad to which the NC pin is connected. Therefore, there has been a problem that static electricity flows through and destroys the semiconductor chips 537a and 537b when static electricity is applied to the NC pin or the dummy input side bonding pad.
(3) While a thermosetting resin for protecting the IC chip is provided around the IC chip, there is a case wherein the resin leaks even to an area connecting the liquid crystal display device and the circuit board on the face of the base film opposite from the face on which the wires are formed, causing a defective connection.
Accordingly, it is an object of the present invention to provide a technology which allows the architrave area, other than the display area, to be reduced further in a liquid crystal display device.
It is another object of the present invention to provide a technology which allows the distance between input and output terminals to be reduced and to prevent the semiconductor chip from being destroyed by static electricity applied from the dummy input side wire or from the dummy input terminal of the semiconductor chip in a liquid crystal driving device.
It is a further object of the present invention to provide a technology which allows the distance between the input and output terminals reduced and to prevent the protecting film to be formed around the semiconductor chip from leaking to the areas of the input and output terminals in a liquid crystal driving device.